Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
  • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
  • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
  • H01B3/42—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes polyesters; polyethers; polyacetals
  • H01B3/421—Polyesters
  • H01B3/422—Linear saturated polyesters derived from dicarboxylic acids and dihydroxy compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
  • C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D163/00—Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D167/00—Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
  • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
  • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
  • H01B3/40—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes epoxy resins

Definitions

• the present invention relates to the preparation of powdered thermosetting compositions based on branched-chain carboxyl groupcontaining polyesters and epoxy compounds, as well as to compositions obtained by this process.
• thermosetting compositions for several years, in the field of paints and varnishes, the use of powdered thermosetting compositions, to replace liquid thermosetting compositions, has met with ever-increasing success, justified by the following reasons:
• thermosetting compositions are, inter alia, widely used for coating domestic electric appliances, bicycles, garden furniture, accessories for the automobile industry, and the like.
• thermosetting compositions are very simple: the powders are applied by means of a spray gun on to the article to be coated, which is a conductor of electricity, with an average potential difference of at least 50,000 volts. For this reason, the particles charged with electrostatic electricity form a regular coating on the article, while the excess powder, which does not adhere to the article because of the insulating effect of the particles already retained, may be recovered.
• the coated article is then heated in an oven where cross-linking of the thermosetting binder of the coating is carried out; in this way, it acquires its final mechanical and chemical properties.
• thermosetting compositions can also be used for the fluidized bed coating technique.
• the article to be coated is heated and introduced into a fluidized bed of particles of the powdered thermosetting composition, so that the fluidized particles which come into contact with the heated article undergo an initial fusion and are retained on the article by adhesion.
• the article thus coated is then heated in an oven to carry out cross-linking of the coating in exactly the same way as in the technique described above using an electrostatic spray gun.
• the present invention particularly relates to those which contain, as binders, carboxyl group-containing polyesters which can be hardened by means of epoxy compounds. More particularly, the present invention relates to a new process for preparing carboxyl group-containing polyesters which are to be hardened by means of epoxy compounds, as well as the carboxyl group-containing polyesters obtained by this process and the thermosetting powdered compositions which can be obtained from these carboxyl group-containing polyesters and epoxy compounds.
• thermosetting coating composition which comprises (1) a polyepoxide resin, the average molecule of which contains, at least two epoxy groups and (2) a solid, modified polyester resin having an acid number from 30 to 100, this acid polyester resin itself being obtained by the reaction of a polybasic organic carboxylic acid anhydride with a hydroxyl group-containing polyester having a hydroxyl number of from 15 to 50, formed from a dibasic aromatic carboxylic acid and at least one dihydric alcohol component selected from aromatic diols, glycidyl esters and dihydric aliphatic or cycloaliphatic alcohols.
• the solid, modified polyester resin having an acid number from 30 to 100 there is first prepared a linear hydroxyl group-containing polyester having a hydroxyl number of from 15 to 50 from a bifunctional acid and at least one dihydric alcohol component, whereafter this hydroxyl group-containing linear polyester is esterified with a polybasic organic acid. It will be seen that the solid, modified polyester resin thus obtained has an acid number which is substantially double the hydroxyl number of the hydroxyl group-containing polyester, i.e. an acid number of from 30 to 100 for a hydroxyl number of from 15 to 50.
• the carboxyl group-containing polyester resins according to the present invention have a branched polymer chain and possess an acid number which has a value substantially equal to that of the hydroxyl number (and not double it).
• a process for the preparation of powdered thermosetting coating compositions suitable for application as paint or varnish on electricity-conducting articles by powder spray methods and fluidized bed coating processes which comprises: in a first stage, preparing a branched-chain hydroxyl group-containing polyester from at least one dicarboxylic organic acid, at least one polycarboxylic aromatic acid and at least one dihydric organic compound; in a second stage, esterifying the hydroxyl group-containing polyester thus obtained with an aromatic or hydroaromatic dicarboxylic acid to give a carboxyl group-containing polyester having an acid number which is substantially equal to the hydroxyl number of the hydroxyl group-containing polyester obtained in the first stage; and in a third stage, homogenously mixing the carboxyl group-containing polyester obtained in the second stage with an epoxy compound containing at least two epoxy groups, and optionally adding auxiliary substances conventionally used in the manufacture of powdered paints and varnishes.
• the dicarboxylic and polycarboxylic organic acids used for the preparation of the branched-chain hydroxyl group-containing polyester may be used in the form of the free acid or their functional derivatives, particularly in the form of the acid anhydride, the acid chloride or an ester of an aliphatic alcohol containing 1 to 4 carbon atoms.
• the dicarboxylic organic acid is preferably a dicarboxylic aromatic or hydroaromatic acid.
• examples thereof include o-phthalic acid, isophthalic acid, terephthalic acid, dihydrophthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid or the like.
• 1 to 15 per 100 equivalents of the carboxyl groups of the dicarboxylic organic acid used in the first stage, 1 to 15, preferably 5 to 10 equivalents of the carboxyl groups may be those of at least one aliphatic or cycloaliphatic acid such as succinic, glutaric, adipic, sebacic, cyclohexane-1,2-dicarboxylic cyclohexane-1,4-dicarboxylic acids or their functional derivatives, the remainder being those of the dicarboxylic aromatic or hydroaromatic acid.
• succinic, glutaric, adipic, sebacic cyclohexane-1,2-dicarboxylic cyclohexane-1,4-dicarboxylic acids or their functional derivatives, the remainder being those of the dicarboxylic aromatic or hydroaromatic acid.
• the aromatic tricarboxylic or polycarboxylic acid may be, for example, trimellitic acid, pyromellitic acid or the like, or their functional derivatives.
• the ratio of carboxyl equivalents of the polycarboxylic aromatic acids to the carboxyl equivalents of the dicarboxylic organic acids used in the first stage is preferably 5:95 to 35:65, more preferably 10:90 to 25:75.
• the dihydric organic compound may be, for example, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, cyclohexane-1,4-dimethanol or the like.
• the amount of the dihydric organic compound relative to the total amount of the organic carboxylic acids used in the preparation of the hydroxyl group-containing polyester is such that the hydroxyl number of the resulting polyester is 50 to 100 mg KOH/g of this polyester.
• the hydroxyl group-containing polyester may be prepared by conventional methods for the synthesis of polyester (cf. Kirk-Othmer, Encyclopaedia of Chemical Technology, 2nd edition, volume 16, pages 159-189, pub. Interscience, New York 1968). Generally speaking, use is made of a conventional reactor equipped with a thermometer, a stirrer, an inlet and outlet for inert gas, a condenser and an azeotropic separator (for example of the Dean-Stark type).
• the dicarboxylic and polycarboxylic acids (or their functional derivatives) and an excess of the dihydric organic compound are introduced into the reactor at the same time, subsequently or portionwise and polyesterification is carried out at a temperature which is gradually increased to about 210° to 220° C., initially at atmospheric pressure and then under reduced pressure, maintaining these operating conditions until a polyester is obtained which has the desired hydroxyl number, which may be between 50 and 100 mg of KOH per g of polyester, and has the desired molecular weight, which may be between 1000 and 3000, according to the reactants employed.
• the hydroxyl group-containing polyester may be removed from the reactor in a molten state and then stored at ambient temperature. However, the hydroxyl group-containing polyester is preferably left in the reactor and the preparation of the carboxyl group-containing polyester is carried out directly.
• the calculated amount of aromatic or hydroaromatic dicarboxylic acid (or anhydride) e.g. any of such acids mentioned above
• polyesterification is continued at a temperature of 170° to 210° C until a carboxyl group-containing polyester is obtained with the desired acid number, which may be between 50 and 100 mg of KOH per g of carboxyl group-containing polyester, and with the desired molecular weight, which may be between 1000 and 3000, according to the reactants employed.
• the carboxyl group-containing polyester is then cast into a thick layer and allowed to cool, whereafter it is crushed to give particles with an average size of from a fraction of a millimeter to a few millimeters.
• the carboxyl group-containing polyester obtained in the previous stage is homogeneously mixed with the epoxy compound, as well as possibly with the various auxiliary substances conventionally used for the manufacture of powdered paints and varnishes suitable for application by powder spray methods and fluidized bed coating processes. Homogenization is carried out, for example, by melting the carboxyl group-containing polyester and the epoxy compound at a temperature lower than that at which a reaction takes place between these two substances, this temperature preferably being within the range of from about 80° C to about 120° C. When complete homogenization has been achieved, the mixture is allowed to cool and is then ground to a powder, the particle size of which is between 0.1 and 250 ⁇ .
• the epoxy compound used above can be a solid monomeric epoxy compound containing at least two epoxy groups, for example, triglycidyl isocyanurate, or a solid polyepoxide resin, for example, the products marketed by "Shell” under the name “Epikote” 1001, “Epikote” 1004, the product marketed by CIBA-GEIGY under the name "Araldite GT 7004" or the like.
• This epoxy compound may be used in an amount of from 0.7 to 1.3, preferably 0.95 to 1.1, equivalents of epoxy groups per equivalent of carboxyl groups in the carboxyl group-containing polyester.
• auxiliary substances which may be added to the powdered thermosetting compositions according to the present invention include, for example, pigments, such as titanium dioxide, yellow iron oxide, red iron oxide, organic dyestuffs or the like, flow control agents, such as Ketonharz (BASF) which is a ketone resin based on cyclohexanone, or Modaflow (MONSANTO) which is a polyethylhexyl acrylate, surface active agents, such as Zonyl-S-13 (E. I. du PONT de NEMOURS & Co.), plasticizers, such as dibutyl phthalate or tributyl phosphate, and/or grinding aids, and the like.
• auxiliary substances are used in their usual effective proportions, it being understood that if the compositions according to the invention are to be used as varnishes, then the addition of auxiliary substances which possess opacifying properties will be omitted.
• Esterification is continued until the acid number is 71 mg of KOH per g polyester and the melt index according to ASTM D 1238/62 T is 33 g in 10 minutes at 125° C using a 2.09 mm die.
• the polyester is then cast at 200° C into a thick film, cooled and ground into granules with an average size of between 0.5 and 2 mm.
• trimellitic anhydride are added and the esterification is continued until the hydroxyl number reaches a value of ⁇ 88 mg KOH per g polyester.
• Esterification of the hydroxyl groups of the branched polyester thus obtained is carried out by introducing into the reactor 397.3 g (2.6 moles) tetrahydrophthalic anhydride.
• the esterification is continued at 210° C until the acid number is 60 mg KOH per g polyester and the melt index is 30 g in 10 minutes at 125° C (2.09 mm die).
• the polyester is then cast into a thick film, as in Example 1.
• polyesters obtained according to the processes of Examples 1 and 2 are formulated as follows into pigmented powders, which can be used in electrostatic powder-spray coating processes:
• the mixtures are ground into particles of 0.1 to 250 ⁇ and are applied to bonderized steel having a thickness of 0.65 mm, using a spray gun, in an electrostatic field at a voltage of 55 KV.
• the thickness of the coating thus formed is 95 microns.
• the steel plate thus coated is then brought to a temperature of 200° C for 20 minutes to enable the coating to cross-link.
• 189 g ethylene glycol, 1076 g neopentyl glycol, 134 g 1,6-hexanediol and 1803 g terephthalic acid are introduced into a 5 liter glass reactor provided with a stirrer and a fractionation column.
• the mixture is heated to 150° C and 1 g dibutyl-tin oxide is added.
• the temperature is gradually raised to 220° C and this temperature is maintained for 7 hours until 415 g water separate off and a clear resin is obtained having a hydroxyl number of 132 and an acid number of 4.
• the mixture is cooled to 170° C and 462 g hexahydrophthalic anhydride are introduced. Esterification is carried out at 210° C giving a hydroxyl group-containing resin having a hydroxyl number of 25 and an acid number of 8.
• trimellitic anhydride 230 g trimellitic anhydride are introduced at 180° C and the temperature of the reaction mixture is raised to 200° C. Polycondensation is continued in vacuo until a carboxyl group-containing resin is obtained having an acid number of 49, a softening temperature of 100°-102° C and a melt index of 24 g in 10 minutes at 125° C.
• a branched-chain hydroxyl group-containing polyester is prepared from 189 g ethylene glycol, 1076 g neopentyl glycol and 134 g 1,6-hexanediol on one hand and 1803 g terephthalic acid and 230 g trimellitic anhydride on the other hand.
• the powders thus obtained are applied to bonderized steel having a thickness of 0.65 mm, using a spray gun, in an electrostatic field at a voltage of 55 KV.
• the thickness of the coating is 60 microns.
• the applied layers are then cured for 15 minutes at 200° C and then subjected to the following tests:
• the delayed gelling of the powder according to the invention offers a considerable advantage, as the varnish layer thus has more time to spread out and results in a flawless taut surface.
• the hydroxyl group-containing resin has an acid number of 14.5 and a hydroxyl number of 30.
• trimellitic anhydride 230 g trimellitic anhydride are then introduced at 170° C and after esterification at atmospheric pressure, heating is continued in vacuo until a melt index of 15 g at 125° C is obtained. At that moment the final carboxyl group-containing resin has an acid number of 55.
• the mixture of glycols mentioned in Example 3 is esterified with 1803 g terephthalic acid.
• a clear resin is obtained with an acid number of 4 and a hydroxyl number of 133.
• This resin is then condensed with 230 g trimellitic anhydride at a temperature of from 170° to 220° C.
• the hydroxyl group-containing polyester resin is esterified until clarification occurs, at atmospheric pressure at maximum 215° C with 498 g isophthalic acid. The reaction is continued in vacuo until the melt index is 19. The final carboxyl group-containing polyester has an acid number of 50.
• the electrostatic powders thus obtained are applied to bonderized steel, under the same conditions as in Example 2, with a thickness of 60 microns. They are subjected to the following tests:
• Example 7 The 880 parts by weight of Araldite GT 7004 of Example 7 are replaced by 940 parts by weight of another polyepoxide resin (Epikote 1004 of SHELL), all other conditions of Example 7 remaining unchanged.
• An electrostatic powder is obtained which gives coatings having pratically the same properties as those obtained with the electrostatic powder described in Example 7.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
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• Spectroscopy & Molecular Physics (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Health & Medical Sciences (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Paints Or Removers (AREA)
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• 1975
  • 1975-04-29 GB GB17740/75A patent/GB1509043A/en not_active Expired
• 1976
  • 1976-04-23 NO NO761393A patent/NO146749C/no unknown
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  • 1976-04-26 DK DK186876A patent/DK186876A/da not_active Application Discontinuation
  • 1976-04-27 MX MX76195U patent/MX3536E/es unknown
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  • 1976-04-28 BR BR2621/76A patent/BR7602621A/pt unknown
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  • 1976-04-28 ES ES447415A patent/ES447415A1/es not_active Expired
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  • 1976-04-28 DE DE19762618729 patent/DE2618729A1/de active Granted
  • 1976-04-28 IT IT49224/76A patent/IT1058250B/it active
  • 1976-04-28 CA CA251,268A patent/CA1068443A/fr not_active Expired
  • 1976-04-28 FR FR7612860A patent/FR2309596A1/fr active Granted
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  • 1976-04-28 CH CH531676A patent/CH606251A5/xx not_active IP Right Cessation
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